The long-range goal of the proposed work is to understand protease gene expression in Schistosoma mansoni. Proteases are utilized by this organism for invasion of the intermediate and definitive hosts and migration through their tissues and for nutrition of the parasite. The proposed work will focus on Smansoni proteases homologus with an adult worm, acidic, thiol hemoglobinase used for degradation of host globin. The specific aims include characterization of schistosome thiol protease gene expression during the parasite's life cycle and determination of the structure of protease genes. Host responses against the native hemoglobinase and recombinant hemoglobinase produced in bacteria will also be evaluated. Characterization of protease gene expression will involve isolation of these enzymes from eggs, cercariae and adults. Biochemical nd immunologic methods will be used to determine gross similarities and differences in enzyme structures and substrate specificities. Localization of the proteases in vivo using immunohistologic techniques will also be performed. Sequencing of cDNAs which encode these proteolytic enzymes will allow determination of protease homologies. Characterization of genes encoding schistosome thiol proteases will include sequencing of coding regions and sequences upstream of the start of transcription. Examination of host immunological responses against the native and recombinant hemoglobinase will be made by immunization of inbred and outbred mice followed by ELISA measurements of antibody titers and examination of delayed hypersensitivity response. Understanding protease gene expression may lead to knowledge of the regulation of expression of schistosome genes, comprehension of mechanisms which underlie transformations during the parasite's life cycle, and the nature of parasitism. Moreover, understanding of proteases at the molecular level may lead to rational approaches to disease control.